Planta

, Volume 231, Issue 4, pp 913–922

Structural and functional changes of PSI-LHCI supercomplexes of Chlamydomonas reinhardtii cells grown under high salt conditions

  • Rajagopal Subramanyam
  • Craig Jolley
  • Balakumar Thangaraj
  • Sreedhar Nellaepalli
  • Andrew N. Webber
  • Petra Fromme
Original Article

DOI: 10.1007/s00425-009-1097-x

Cite this article as:
Subramanyam, R., Jolley, C., Thangaraj, B. et al. Planta (2010) 231: 913. doi:10.1007/s00425-009-1097-x

Abstract

The effect of high salt concentration (100 mM NaCl) on the organization of photosystem I-light harvesting complex I supercomplexes (PSI-LHCI) of Chlamydomonas reinhardtii was studied. The electron transfer activity was reduced by 39% in isolated PSI-LHCI supercomplexes. The visible circular dichroism (CD) spectra associated with strongly coupled chlorophyll (Chl) dimers were reduced in intensity, indicating that pigment–pigment interactions were disrupted. This data is consistent with results from fluorescence streak camera spectroscopy, which suggest that red-shifted pigments in the PSI-LHCI antenna had been lost. Denaturing gel electrophoresis and immunoblot analysis reveals that levels of the PSI reaction center proteins PsaD, PsaE and PsaF were reduced due to salt stress. PsaE is almost completely absent under high salt conditions. It is known that the membrane-extrinsic subunits PsaD and E form the ferredoxin-docking site. Our results indicate that the PSI-LHCI supercomplex is damaged by reactive oxygen species at high salt concentration, with particular impact on the ferredoxin-docking site and the PSI-LHCI interface.

Keywords

Chlamydomonas Excitation energy Light harvesting complexes PSI-LHCI supercomplexes Photosystem I core Reactive oxygen species Salt stress Superoxide dismutase 

Abbreviations

CD

Circular dichroism

Chl

Chlorophyll

DDM

n-Dodecyl-β-maltoside

LHC

Light harvesting complex

MALDI-TOF

Matrix assisted laser desorption ionization time-of-flight mass spectrometry

PS

Photosystem

SOD

Superoxide dismutase

Copyright information

© Springer-Verlag 2010

Authors and Affiliations

  • Rajagopal Subramanyam
    • 1
    • 2
    • 3
  • Craig Jolley
    • 4
    • 5
  • Balakumar Thangaraj
    • 3
  • Sreedhar Nellaepalli
    • 1
  • Andrew N. Webber
    • 2
  • Petra Fromme
    • 3
  1. 1.Department of Biochemistry, School of Life SciencesUniversity of HyderabadHyderabadIndia
  2. 2.The Center for Bioenergy and Photosynthesis, School of Life SciencesArizona State UniversityTempeUSA
  3. 3.Department of Chemistry and Biochemistry, The Center for Bioenergy and PhotosynthesisArizona State UniversityTempeUSA
  4. 4.Department of Physics, The Center for Bioenergy and PhotosynthesisArizona State UniversityTempeUSA
  5. 5.Department of Chemistry and BiochemistryMontana State UniversityBozemanUSA